Cor triatriatum is a rare congenital malformation. Symptoms mimic a mitral stenosis. The combination of a cor triatriatum and mitral stenosis is less common. Some very rare cases of intraoperative findings were described. We report the case of a woman of 38 years, came to consultation for exertional dyspnea progressively worsening and palpitations during exercise. Clinical examination found mainly irregularity of the heart sounds, diastolic mitral murmur 3/6, an accentuated pulmonary component of the second heart sound. The electrocardiogram showed an atrial fibrillation and right ventricular hypertrophy. Echocardiogram concluded a cor triatriatum with a patent foramen ovale, associated with rheumatic mitral stenosis tight and severe pulmonary hypertension.